Lt Medium

Johnson Starley Lt Fault Code

Also written as LT — same fault.

The Johnson Starley Lt fault code means: your heater is temporarily turning itself off because it is getting too hot and needs to cool down to prevent damage.. It appears on 2 Johnson Starley models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Heater will shut off the burner in order to limit the warm air temperature.
Typical repair cost £80-160 (including labour)

DIY fix possible

Check all warm air vents throughout the house to ensure they are fully open and not obstructed by furniture or curtains.Inspect the air filter and clean or replace it if it is clogged with dust.Ensure the return air grille is clear and not blocked by household items.

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Johnson Starley models that show the Lt fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Johnson Starley Lt fault code information on this page is sourced and cross-checked against the official Johnson Starley service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026